M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)

Analysis - TIMÁR-BALÁZSY Ágnes: Investigation of dyes on textiles from the collections of Hungarian museums

Minor) and occidental kermes (from Spain), which may refer to the spead of the cochineal insect after the discovery of America [8]. Formularies in the 17th century in fact, repeat the substances and techniques contained in Rosetti's book, the difference being that red sandalwood, fustic and logwood appear among the dyes. Macquer gives an account in 1759 on how Prussian blue prepared by himself is suitable for dyeing silk [9]. In 1749 Brancroft gives information about dyeing with the bark of quercitron [10]. The most important Hungarian manuscripts of dyeing recipes from the 18th, 19th c. provide recipes for dyeing by indigo carmine which was discovered in 1740 [11,12]. From several publications of the 19th century we can get information on chrome yellow and chrome orange (1809), antimony orange (1842), picric acid (1845), and on murexid (1853), and the mauve (1856), the fuchsin (1858), and the other synthetic dyes that appear on the dyer's palette [13,14,15]. As a consequence of the above mentioned facts it is clear that identification of dyes with known dates in European use provides an opportunity for identifying the age of textiles and revealing forgeries. 1.2. Getting an insight into the „original" colour scheme of the object It is often claimed by museologists that one can learn about the original colour of textiles on the basis of the analyses of dyes. In some cases, hypotheses on the original colour can be proved; e .g. in the case of medieval tapestries — which have too much blue colour today — we can often trace yellow dyes proving the original green colour of the thread. The same can be said about faded beige threads dyed with orchil; we can be sure that the original colour was somewhere between pink and purple. Even in the case of completely faded textiles the determination of the dyestuff can be successful. Walton [16] and Taylor [17] published considerable results on the dyes of archaeological textiles, or at least on their being dyed. We had evidence on the determination of dyes on the sewing thread, when all traces of colouring had already disappeared from the garment [18]. Such evidence can also serve as important information to museologists. In spite of the fact that the examination of dyes takes us nearer to the original colour scheme of the object, all estimations should be done with due caution. Most of the natural dyes applied to textiles are "mordant-dyes" ,this means that the textile was treated before, during of after dyeing with the solution of certain metallic salts (water soluble salts of aluminium, zinc, copper, iron, etc.). The application of mordant not only prevents the dyed textile from bleeding but gives different colours with the same dyestuff depending on the applied metallic salt. We can give an example on this after the recipe book of Hellot fcom 1750: cochineal gives crimson on alum, scarlet on tin, dark violet on zinc, purple on iron, violet on lead, dove-grey on bismuth, claret on copper, cinnamon on silver, and iridescent brown on gold mordant [19]. Thus if we can determine the metallic ion of the mordant we can estimate the original colour more precisely, even so the exact shade will be dubious. 13. Planning the appropriate cleaning and conservation method Not only the bleeding but the change of colour of the dyed yam or textile can be estimable in the knowledge of the result of dye analysis. On the basis of the chemical structure of the dye its behaviour at various pH values can be characterized.